package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {
    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    public void set(String key, Object value, Long time, TimeUnit timeUnit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, timeUnit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit timeUnit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(timeUnit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R, ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit timeUnit) {
        //1.从redis中查询缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断缓存是否命中
        if (StrUtil.isNotBlank(json)) {
            //3.命中
            return JSONUtil.toBean(json, type);
        }

        if ("".equals(json)) {
            //返回错误信息
            return null;
        }
        //5.根据id查询数据库
        R r = dbFallback.apply(id);
        //6.判断商铺是否存在
        //7.不存在，返回404，结束
        if (r == null) {
            //将空值写入redis，防止缓存穿透
            stringRedisTemplate.opsForValue().set(key, "", 2L, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //8.存在，将商铺数据写入redis
        this.set(key, JSONUtil.toJsonStr(r), time, timeUnit);

        //9.返回商铺信息，结束
        return r;
    }

    private final static ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback,Long time,TimeUnit timeUnit) {
        //1.从redis中查询缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断缓存是否命中
        if (StrUtil.isBlank(json)) {
            //3.未命中
            return null;
        }
        //4.命中，需要把json反序列化成对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，返回商铺信息
            return r;

        }
        //5.2过期，则需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean tryLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if (tryLock) {
            //6.3成功，开启独立线程，实现缓存重建
            String s = stringRedisTemplate.opsForValue().get(key);
            RedisData redisData2 = JSONUtil.toBean(s, RedisData.class);
            R r2 = JSONUtil.toBean((JSONObject) redisData2.getData(), type);
            LocalDateTime expireTime2 = redisData2.getExpireTime();
            if (expireTime2.isAfter(LocalDateTime.now())) {
                return r2;
            }
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,timeUnit);

                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺数据
        return r;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10L, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }

}
